Method for producing cavitied rubber sheeting



June 9, 1942. .1. U. MANN 2,285,526

METHOD FQR PRODUCING CAVITIED RUBBER SHEETING Filed May 15, 1959 IINVENTOR JAM/f6' 0. AMA/Af ATTORNEYS the number and arrangement of thepits pre| Patented June 9, i942 METHQD FOR. PRODUCING CAVITIED RUBBERSHEETING .lames U. Mann, Arlington, N. J., assignor to United StatesRubber Company, New York, N. Y., a corporation of New Jersey ApplicationMay- 13, 1939, Serial No. 273,470

(ci. 154-2) l 4 Claims.

This invention relates to methods of producing cavitied rubber sheetmaterial and more particularly to methods of making rubbersheet materialhaving a desired number and arrangement and dimensions of pits orcavities in the surface thereof. This invention is especiallyadvantageous in making any number of replicas of a master cavitieddeposition backing or blanket in which the size andarrangement of pitsor cavities in each replica are identical with all the others.

g According` to United States Letters Patent No.y

2,032,942, a latexcomposition is-spread onto an Y air impermeabledeposition backing or blanket having cavities or pits in its uppermostsurface so as to entrap air within the cavities or pits of thedeposition blanket. By the application of' heat to the blanket, the thusentrapped air ls caused to expand and force its way through the Wetlatex. coating, While at the same time the latex coating is caused todry or gel so as to render permanent the perforations in the spread filmof latex composition. These spreading and heating operations may berepeated until the desired total thickness of perforate rubber sheet hasbeen builtup. After the final drying, the

perforate rubber sheet is stripped from the blanket and then vulcanized.

While various deposition blankets and methods of making them aredescribed in the above cited patent; the preferred backing' is made bycoating a woven fabric, such as 4.75 cotton sheeting@ withrubber latexin such a manner that the meshes of the fabric are closed on one side ofthe fabric and are open onthe other side, and the individual intersticesare also sealed on. each from the other. bythe coating of the.threads-to provide a multitude of pockets opening on the depositionsurface of the fabric. A deposition blanket so made ,hasv provensatisfactoryV for making a limite'dquantity ofrubber `films or sheets,but upon its wearing out or being de'- faced'the blanket must bereplaced by another blanket preparedjfrom another and different piece offabric. .As a consequence it is diflicult ent in the surface of a masterdeposition blanket which may have been made according to the. processdescribed in the above previously cited patent, or by any other suitableprocess. Any desired number of identically cavitied deposition backingsmay be vproduced without the disadvantages and dimculties mentioned. Inpracticing the invention, a cavitiedldeposition surface is spread with afilm of .latex composition,

and the latex film thereby deposited is at least partially dried orgelled and concurrently therewith is' pierced with1 a plurality of fluidjets to form permanent perforations therein. A perforate rubbersheet ofthe desired thickness may be built up by carrying out the aboveoperations the requisite number of times. On the upper surface of thissheet, one or more films of latex composition are then spread sofas tobridge and seal on the perforations formed; in the lower strata, andthis final film (or filmsl is dried to form a fluidimpervious continuoussealing filmy or layer. A sheet of woven fabric or other equivalentinextensible reinforcing material may then be ad hered to the sealingfilm or films either by rolling the fabric down into a wet film offreshly spread latex or rubber cement or by passing the fabric through'a bank of latex and under either'a doc- `tor blade or -a helicallygrooved cylindrical to prepare a replacement vblanket which is ldenticalwith the previous one. described preparation of such blankets is adifilcult process, entailing a great dealof careto avoldthe preparationofimperfect blankets which must. of course, be discarded.

The present invention provides a method of manufacturing, atrelatively/low cost, replica deposition blankets which reproducefaithfully Furthermore, the

spreader bar. Other suitable methods of doubling a fabric to a spreadsheet of latex rubber may be used conveniently.- After the fabricreinforcement has been adhered to the deposition surface one or moreadditional films of latex rubber may,- if desired, be spread thereonanddried to complete the production of an lnextensiy ble cavitiedsheet. Thecavitied sheet may then be removed from the deposition surface uponwhich it was formed and vulcanized, and the cavitied' surface thereofmayk be treated, as -by chlorination or oxidation, to render latexsubsequently deposited thereon easily removable therefrom after it hasdried orgelled, The rev4sultant cavitied rubber sheet provides aninitial master deposition blanket for the production of others identicalto it, andthe procedure may berepeated as many times as desired, so thatthe cavities in each rubber sheet deposited thereon will besubstantially identical in site and arrangement to those in every otherperi'orat'e sheet formed therefrom.

By the present invention the possibility of er-` ror in reproducingreplica blankets identical with the originals is reduced to a minimum.Af'terthe perforate pliesof the blanket 4have been produced, and theimperforate ply has been deposshowing partial removal Fig. 2 -from thebacking on which it is produced.

layer l. 0n the backing may be produced as follows: A hlm or 'cation ofsufficient heat ited thereon, it may readily be determined merely byinspection whether the imperforate plies have succeeded in sealing offall the perforations in the outermost perforate ply. In the manufactureof cavitied deposition blankets heretofore in the fact that the entiredeposition blanket is built` up in a continuous series of operationswithout the necessity of removing the perforate sheet material from thebacking and thereby subjecting it to folding or stretching. VTheapplicaltion of an inextensible ply of reinforcing material reduces thepossibility of distortion during removal.

The drawing illustrates diagrammatically, on a greatly enlarged scale, aseries -of steps in the Another render the vulcanized surfacenon-adherent to rubber deposited thereon from latex.

For the production of a series of replica samples, the process may becarried out as shown in Figs. 2 and 3. Accordingly,l a layer Il of latexcomposition is deposited on the upper surface t bridge over and seal oilthe perforations I5, and 1 is dried without being perforated. Thereplica production of identically cavitied rubber sheets y according tothe present invention, in which:

Fig. l is a greatly enlarged cross-sectional view of a master cavitiedsheet produced according to the invention on a conventional depositionbacking;

Fig. 2 is a greatly enlarged cross-sectional view of replica cavitiedsheet produced from the master: and

Fig. 3 is a greatly enlarged cross-sectional view Referring tothedrawing,vFig. 1 shows the formation of a cavitied rubber sheet on aconventional backingl comprising woven threads 2 individuallyimpregnated-and/or coated with a rubber fllm 3 and secured to a rubberbacking backing I a similar master layer i of latex is spread onto thebacking I to entrap air inthe pits or cavities between the threads 2,and the backing I and film 6 are f heated to expand the thus entrappedair sufficiently to form perforations 1 while at the same time therubber inthe film 6 is caused to gel or dry. This process is 'repeateduntil a perforate rubber layer 8 of the desired thickness is built upand dried. Before or after' completion of the drying of the layer I, theupper surface 9 thereof-is coated with one or more films I0 which may beof the samelatex composition as that in the j layer 8. This ilnalnlm (orfilms) is dried under conditions which d o not effect piercing of therubber covering over perforations 1. For example, f the drying orgelling ofthefilm III maybeaccomplished at to appreciably expand theentrapped air. The film Il provides a fluidimpervious -and continuousrubber seal which n closes ofi' the perforations. A reinforcing orstiifening base ply II comprising, for example, one or more fabriclayers I2 bonded with rubber, may beA secured to the outer surface ofthe backing l. After drying 4the replica' blanket I may be stripped fromthe deposition blanket I and vulcanized. This vulcanized surface of theinitial layer 8 may be haiogenated and hardened by treatment with, forexample, a 'W2% solution of sulphur chloride in carbon tetrachloride,followed by a treatment with a 2 to 3% solution of bromine, in thecarbon tetrachloride; or with the bromine solution alone; or in anydesired manner, of which many are known in the; art, to

of the sheet formed in room temperature without the'appli blanket I3 maythen be withdrawn from the blanket 5, as shown in Fig. 3, before orafter application of a reinforcing ply, and may be vulcanized andtreated as above described. Inl this manner as many identical blanketsas maybe desired can be produced either from the original blanket 5 orfrom any of the replica blankets I3.

While a particular method of producing ,the original blanket has beendescribed, it may be produced upon an original perforate base instead ofthe air impermeable cavitied base employed in the method described. Inthis embodiment, a film of latex is spread in the ordinary manner tobridge the perforations, and a Jet of uid is forced through eachperforation in the base to pierce the spread film. Asthe film is piercedto form perforations therein, the latex immediately surrounding theperforations may be set by heating if no coagulant is used, or byemploying, as the jet.of uid, a coagulant for latex. The gelling ordrying ofthe remainder of the pierced nlm may thenbe completed in anydesired manner. A convenient method for carrying out this' stage in theprocess is described in United States Letters Patent 2,032,923. Afterthe desired number of superimposed perforate films have been produced inthis way, the nal sealing film or films are deposited thereon, as abovedescribed, that is, under conditions which gel or dry the final filmorffilmsbut do not produce perforations therein. In this particularembodiment of the invention, heat may be employed to gel or dry thefinal layers without danger of expanding the air in theperforations-therebelow, since that air in this case is not confined orentrapped.

I'he term latex as employed in this speciflcation and the appendedclaims designates broadly coagulable dispersions of rubber orrubber-like materials as well as natural latex, which may be preservedor compounded or` otherwise treated as desired, as by vulcanization, andwhich may be in normal, concentrated, diluted, or purified conditionproduced by methods well known in the art.

While certain present preferred methods of practicing the invention havebeen described, it

may be understood that it may be otherwise prac.- V

ticed as will occur to those skilled .in the artand within the spirit ofthe inventio and is to be limited only by the'scope of the appendedclaims.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

l. The method of making a rubber sheet havving cavities in the surfacethereof which comprises depositing a lm of latex composition onto adeposition blanket, concurrently drying or gelling said vfilm andpiercing said film with a plurality of fluid jets to form permanentperforations therein, depositing a lm of latex :onto said film andconcurrently drying or gelling and piercing said second named 4film,repeating said 2,285,526 operations until a perforate rubber sheet isbuilt itied, built-up blanket from the first-named.

deposition blanket.

2. A process for manufacturing a rubber sheet having cavities in thesurface thereof which comprisesspreading a coating of latex compositiononto an air-impermeable deposition `blanket having cavities or pits inthe deposition surface thereof so as to entrap air between the latexcoating and the backing in the said'cavities or pits, and heating thebacking to cause the entrapped air to expand and force its Way throughthe latex coating while it is drying or gelling to form permanentperforations therein, depositing a lm of latex onto said coating andconcurrently drying or gelling and piercing said second named lm,repeating said operations until a perforate rubber sheet is built up,and thereafter spreading a i'llm of latex composition upon saidperforate sheet to bridge over and thereby seal exteriorly, withoutfilling up, an opening of each perforation, drying or gelling said filmso that it remains imperforate, and removing the cavitied,

built-up blanket from the first-named cavitied deposition blanket.

3. The method. of making a rubber sheet having cavities in the surfacethereof which comprises depositing a nlm of latex a deposition blanket,concurrently drying' or gelling said nlm and piercing said nlm with aplurality offluid jets to form permanent perforations therein,depositing a iilmof latex onto said film and concurrently drying orgelling and piercing said second named film, repeating said operationsuntil aperforate rubber -sheet is built up, and thereafter depositing asealing lm of latex composition onto said perfora e rubber compositiononto sheet to bridge over and thereby seal exteriorly, withoutlling up,an opening of each perforation, drying or gelling said sealing lm sothat i it remains imperforate, removing the cavitied sheet from theblanket, and rendering the cavitied surface of said sheet -non-adherentto an in situ solids deposit of a latex composition; substantially inthe manner set forth.

4. The method of making a rubber sheet having cavities in thesurfacethereof which comprises the step of deposizing a. film of latexcomposition onto a deposition blanket, the step of concurrently dryingor gelling said iilm and piercing said film with a plurality of uidjetsto form permanent perforations therein, the step of depositing a film oflatex onto said film and concurrently drying or gelling and piercingsaid second named film, repeating said operations until a perforaterubber sheet is built up, and the step of depositing a sealing lm oflatex composition onto said perforate rubber sheet to bridge over andthereby seal exteriorly', without lling up, 'an opening of eachperforation, and the step of securing a ply of reinforcing material tovsaid sealing layer, said steps being performed in the order named as acontinuous series of operations while the built-up sheet remains inplace upon the deposition blanket, and -thereafter removing thereinforced cavitied sheet from said deposi.

tion blanket.

JAMES U. MANN.

